International Journal of Scientific and Research Publications, Volume 2, Issue 12, December 2012 1 ISSN 2250-3153

www.ijsrp.org

Machining Parameters Optimization of WEDM Process

Using Taguchi Method

Jaganathan Pa, Naveen kumar T

b, Dr. R.Sivasubramanian

c

aResearch scholar, Department of Mechanical Engineering, Coimbatore institute of technology, Coimbatore 641014, India

bAsst professor, Department of Mechanical Engineering, RVS Faculty of Engineering, Coimbatore 641402, India c Professor, Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore 641014, India

Abstract- WEDM is a widely recognized unconventional

material cutting process used to manufacture components with

complex shapes and profiles of hard materials. In this thermal

erosion process, there is no physical contact between the wire

tool and work materials. Wire Electrical Discharge Machining

(WEDM) is getting more tasks in fields like dies, punches, aero

and many more. It is the very difficult task to get optimum

process parameters for higher cutting efficiency. Accuracy is

becoming a predominant factor nowadays. In this paper EN31 is

taken for study. The design of experiments (DOE) is done in

taguchi L27 orthogonal array (OA). In WEDM process rough

machining gives lesser accuracy and finish machining gives fine

surface finish, but it reduces the machining speed. Hence we

have to improve the MRR and reduce the Ra as the objective,

which is done by taguchi method.

Index Terms- WEDM,DOE, Orthogonal array,MRR,Ra,Taguchi

method

I. INTRODUCTION

n this paper, Machining parameter of the WEDM process can

be optimized by using taguchi method. Taguchi method is

based on “ORTHOGONAL ARRAY’’. It provides a set of well

balanced experiments, which gives much reduced “variance’’ for

the experiment with “optimal setting’’ of control parameters.

J.L. Lin et al [1] the application of the taguchi method with

fuzzy logic for optimizing the electrical discharge machining

process with multiple performance characteristics has been

reported. The machining parameters (the work piece polarity,

pulse-on time, duty factor, and open discharge voltage, discharge

current and dielectric fluid) are optimized with considerations of

the multiple performance characteristics (electrode wear ratio

and material removal rate). Nihat Tosun et al [2] find on the

effect and optimization of machining parameters on the notch

and material removal rate (MRR) in wire electrical discharge

machining (WEDM) operations. The experimental studies were

conducted under varying pulse duration, open circuit voltage,

wire speed and discharge flushing pressure. The settings of

machining parameters were determined by using taguchi

experimental design method. Can Cogun [3] the settings of

machining parameters were determined by using taguchi

experimental design method. The level of importance of the

machining parameters on the kerf and the MRR is determined by

using ANOVA. The highly effective parameters on both the kerf

and the MRR were found as open circuit voltage and pulse

duration, whereas wire speed and dielectric flushing pressure

were less effective factors. Amar Patnaik et al [4] Introducing

zinc coated copper as electrode tool with the process parameters

of discharge current, pulse duration, pulse frequency, wire speed,

wire tension, dielectric flow rate. By using factors, maximization

of MRR and minimization of surface roughness is done in

WEDM process using taguchi method. Tanimura et al [5]

projected new EDM process using water mist, which requires no

tank for the working fluid. They also pointed out that the mist-

EDM/WEDM enables non-electrolytic machining even, when

electrically conductive water is used as the working liquid. Fu-

chen Chen et al [6] Research is based on fuzzy logic analysis

coupled with taguchi methods to optimize the precision and

accuracy of the high-speed electrical discharge machining

(EDM) process, pulse time, duty cycle, peak value of discharge

current as the most important parameters, powder concentration,

powder size are found to have relatively weaker impacts on the

process design of the high speed EDM. The most important

factors affecting the precision and accuracy of the high-speed

EDM process have been identified as pulse time, duty cycle, and

peak value of discharge current. Dry EDM has many advantages

such as, extremely low tool wear ratio, higher precision, smaller

heat affected zone. The experimental studies were conducted

under varying pulse duration, open circuit voltage, wire speed

and dielectric flushing pressure. H.Singh et al [7] analyze the

effects of various input process parameters like pulse on time,

pulse off time, gap voltage, peak current , wire feed and wire

tension have been investigated and impact on MRR is obtained.

Finally they reported MRR increase with increase in pulse on

time and peak current. MRR decrease with increase in pulse off

time and servo voltage. Wire feed and wire tension has no effect

on MRR. A.K.M. Nurul Amin et al [8] Conducting experiments

on cutting of tungsten carbide ceramic using electro-discharge

machining (EDM) with a graphite electrode by using taguchi

methodology. The taguchi method is used to formulate the

experimental layout, to analyze the effect of each parameter on

the machining characteristics, and to predict the optimal choice

for each EDM parameter such as peak current, voltage, pulse

duration and interval time. It is found that these parameters have

a significant influence on machining characteristic, such as metal

removal rate (MRR), electrode wear rate (EWR) and surface

roughness (SR). The peak current significantly affects the EWR

and SR, while, the pulse duration mainly affects the MRR.

Taguchi method has been used to determine the main effects,

significant factors and optimum machining condition to the

performance of EDM. Kuo-Wei Lin et al [9] conduct test Wire

Electrical Discharge Machining (WEDM) of magnesium alloy

I

International Journal of Scientific and Research Publications, Volume 2, Issue 12, December 2012 2

ISSN 2250-3153

www.ijsrp.org

parts via the taguchi method-based gray analysis was conducted,

they considered multiple quality characteristics required include

material removal rate and surface roughness following WEDM.

This work machines magnesium alloy parts under controlled

machine parameter settings, and measures the above quality

characteristics. The optimized machine parameter settings clearly

improve quality characteristics of the machined work piece

compared to quality levels achieved for initial machine parameter

settings. The complex interactions in WEDM involve wire feed

rate, pulse-on time, pulse-off time, no load voltage, servo

voltage, and wire tension. Kamal Jangra et al [10] Investigated

on Influence of taper angle, peak current, pulse-on time, pulse-

off time, wire tension and dielectric flow rate are investigated for

material removal rate (MRR) and surface roughness (SR) during

intricate machining of a carbide block. In order to optimize MRR

and SR simultaneously, grey relational analysis (GRA) is

employed along with taguchi method. WC-Co composite is

studied, grey relational analysis (GRA) is employed along with

taguchi method, the percentage error between experimental

values and predicted results are less than 4% for both machining

characteristics.

Table.1 Parameters of the setting

Control

factors

Symbols Fixed

parameters

Applied

voltage

Factor -A Wire Molybdenum

wire

Pulse width Factor- B Shape Rectangular

product

Pulse

interval

Speed

Factor -C

Factor- D

Location of

work piece on

work table

At the centre of

the table

Thickness of

work piece

8 mm

Stability Servo control

Height of work

piece

50 mm

Wire type Molybdenum

wire, Diameter

0.20 mm

Table.2 Levels for various control factors

Factors Levels

Control factors I II III Units

A. Applied

voltage

75 90 105 Volts

B. Pulse width 3 4 5 µs

C. Pulse interval 20 25 30 µs

D. Speed 250 500 750 Rpm

II. EXPERIMENTAL DATA COLLECTION

This section describes the experimental setup, explains the

method of conducting experiments, and design of experiment

based on Taguchi method.

2.1. Experimental set up

Experiments were conducted on ST CNC-E3 (MCJ) wire

cut EDM machine. It was made by Steer Corporation this

machine is numerically controlled wire EDM machine. The X

and Y axis of the table movement can be controlled by using

servo controller. In X axis the table will move at a distance of

300 mm and in Y axis the table will move at a distance of 250

mm. According to the convention of normal polarity, the work-

piece is connected to the positive terminal of the source and the

tool is attached to the negative terminal of the source.

Fig. 1 Experimental setup

Figure 1 shows that arrangement of wire cut EDM machine

the experimental data based on the DOE were collected to study

the effect of various machining parameters of the EDM process.

These studies had been undertaken to investigate the effect of

applied voltage, discharge current, pulse width, pulse interval on

the Metal removal rate and surface roughness.

2.2. Experimental procedure

The experiments were conducted on EN 31 alloy steel

material having composition of (1.00% C, 0.50% Mn, 1.40% Cr,

and 0.20% Si.) as a work specimen. The work piece is in the

form of rectangle plate having dimensions of mmmmmm 850100 Work piece had been machined using

molybdenum wire is used as a tool having diameter of 0.20mm

and de-ionized water as a dielectric fluid. Each sample had been

machined for a length of 4mm. Machining time were measured

using a stop watch. After machining to calculate the MRR and

Ra values were measured using Mitutoyo SJ.201P surface tester.

Meter has a stylus stroke of 350µm, resolution of 0.01 µm,

minimum cut-off of 0.25mm and 2µm stylus radius was used.

The measurement length was set to 3mm.

International Journal of Scientific and Research Publications, Volume 2, Issue 12, December 2012 3

ISSN 2250-3153

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2.3 Design of experiment based on Taguchi method

Table.3 Experimental design using L27 orthogonal array

S.

N

O

A B C D MRR

(mm3/

min)

S/N Ratio

(db)

Ra

(mµ)

S/N

Ratio

(db)

1 1 1 1 1 3.315 10.4097 3.32 -10.4228

2 1 1 2 2 4.975 13.9359 3.31 -10.3966

3 1 1 3 3 2.663 8.507423 3.13 -9.91089

4 2 2 1 2 7.889 17.94044 3.64 -11.222

5 2 2 2 3 7.206 17.15389 3.42 -10.6805

6 2 2 3 1 3.810 11.6185 3.42 -10.6805

7 3 3 1 3 11.40 21.1381 3.65 -11.2459

8 3 3 2 1 6.932 16.81717 3.59 -11.1019

9 3 3 3 2 5.649 15.03943 3.75 -11.4806

10 2 3 1 2 7.130 17.06179 3.5 -10.8814

11 2 3 2 3 7.144 17.07883 3.41 -10.6551

12 2 3 3 1 7.024 16.93169 3.71 -11.3875

13 3 1 1 3 6.969 16.86341 3.37 -10.5526

14 3 1 2 1 4.002 12.04554 3.56 -11.029

15 3 1 3 2 4.580 13.21731 3.46 -10.7815

16 1 2 1 1 4.527 13.11621 3.32 -10.4228

17 1 2 2 2 2.257 7.070631 3.42 -10.6805

18 1 2 3 3 6.130 15.74921 3.34 -10.4749

19 3 2 1 3 7.999 18.06071 3.45 -10.7564

20 3 2 2 1 5.664 15.06246 3.46 -10.7815

21 3 2 3 2 4.898 13.80038 3.46 -10.7815

22 1 3 1 1 4.181 12.4256 3.49 -10.8565

23 1 3 2 2 6.083 15.68236 3.63 -11.1981

24 1 3 3 3 5.690 15.10225 3.31 -10.3966

25 2 1 1 3 3.892 11.80346 3.32 -10.4228

26 2 1 2 2 5.872 15.37572 3.2 -10.103

27 2 1 3 1 3.657 11.2625 3.24 -10.2109

The experiment is carried out on ST CNC-E3 (MCJ) wire

cut EDM machine, the input parameters range can be given as

input based on literature survey. Then machining the specimen

using WEDM machine and measureable values can be recorded

to evaluate the effects of machining parameters on performance

characteristics (MRR, and Ra) and to identify the performance

characteristics under the optimal machining parameters.

III. RESULT AND DISCUSSION

Figures 2, 3 shows graphically the effect of the four control

factors on MRR, Ra. By using MINITAB 16 software the effect

of control factors can be predicted.

Fig. 2 Effect of control factors on MRR

Fig. 3 Effect of control factors on Ra

The S/N ratio response table and response graphs are

shown for S/N ratio for MRR in Table 3 and Fig. 2 respectively.

Similarly, response table and response graphs are shown for S/N

ratio for Ra in Table 3 and Fig. 3 respectively. Analysis of the

result leads to the conclusion that factors at level A3, B3, C1, D3

gives maximum MRR. Although factors C factor is not show

significant effect on material removal rate and surface finish as

shown in Fig. 2. Factor C is having least significance effect for

improving MRR. Similarly, it is recommended to use the factors

at level A3, B3, C1, D2 for minimization of Ra as shown in Fig.

3. Factors C and D have least contribution for minimization of Ra

IV. CONFORMATION TEST

The optimal combination of machining parameters has been

determined in the previous analysis. However, the final step is to

predict and verify the improvement of the observed values

through the use of the optimal combination level of machining

parameters. The estimated S/N ratio for MRR and Ra are shown

in table 4&5.

Table 4 S/N ratio response table for MRR

A B C D

Level 1 12.44

12.60 15.42 13.30

Level 2 15.14

14.40 14.47 13.95

International Journal of Scientific and Research Publications, Volume 2, Issue 12, December 2012 4

ISSN 2250-3153

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Level 3 15.78 16.36 13.47 16.11

Delta 3.34 3.76 1.95 2.82

Rank 2 1 4 3

Table 5 S/N ratio response table for Ra

A B C D

Level 1 -10.53 -10.43

-10.75 -10.77

Level 2 -10.69 -10.72

-10.74 -10.87

Level 3 -10.95

-11.02 -10.68 -10.53

Delta 0.42 0.60 0.08 0.34

Rank 2 1 4 3

The predicted and experimental value comparison for MRR

and Ra from the optimal values by Minitab16 is shown in tables

6&7.

Table 6 Results of the confirmation experiment for MRR

Optimal machining parameter

Prediction Experimental

Level A3B3C1D3 A3B3C1D3

MRR(mm3/min) 9.57367 9.611

Table 7 Results of the confirmation experiment for Ra

Optimal machining

parameter

Prediction Experimental

Level A3B3C1D2 A3B3C1D2

Ra(µm) 3.15556 3.12

V. CONCLUSION

In this article, an attempt was made to determine the

significant machining parameters for performance measures like

MRR and Ra separately in the WEDM process. Factors like

Voltage, Pulse width and Speed have been found to play a

significant role for MRR and surface roughness. Taguchi’s

method is used to obtain optimum parameters combination for

maximization of MRR and minimization of Ra. The

conformation experiments were conducted to evaluate the result

predicted from Taguchi Optimization.

REFERENCES

[1] J.L. Lin, K.S. Wang, B.H. Yan, Y.S. Tarng (2000), Optimization of the electrical discharge machining process based on the Taguchi method with fuzzy logic. Journal of Materials Processing Technology 102 (2000) 48-55

[2] Nihat Tosun C. Cogun and H. Pihtili (2004) a study on kerfs and material removal rate in wire electrical Discharge machining based on Taguchi method. Journal of Materials Processing Technology 152 (2004) 316–322

[3] Can Cogun (2004) a study on kerf and material removal rate in wire electrical discharge machining based on Taguchi method. Journal of Materials Processing Technology.

[4] S. S. Mahapatra, Amar Patnaik, (2006) Optimization of wire electrical discharge machining (WEDM) process parameters using Taguchi method. International Journal of Advanced Manufacturing Technology.

[5] Tanimura (2006) Taguchi and Gauss elimination method. A dual response approach for parametric optimization of CNC wire cut EDM of PRAlSiCMMC, A. International Journal of Advanced Manufacturing Technology (2006) 28: 67–75

[6] Yih-fong Tzeng, Fu-chen Chen (2007). Multi-objective optimisation of high-speed electrical discharge machining process using a Taguchi fuzzy-based approach, Materials and Design 28 (2007) 1159–1168

[7] H. Singh, R. Garg (2009) Effects of process parameters on material removal rate in WEDM, Journal of achievements in material and manufacturing engineering, Volume 32, Issue.

[8] Mohd Amri Lajis, H.C.D. Mohd Radzi, A.K.M. Nurul Amin (2009) The Implementation of Taguchi Method on EDM Process of Tungsten Carbide. European Journal of Scientific Research, ISSN 1450-216X Vol.26 No.4 (2009), pp.609-617

[9] Kuo-Wei Lin, Che-Chung Wang (2010), Optimizing Multiple Quality Characteristics of Wire Electrical Discharge Machining via Taguchi method-based Gray analysis for Magnesium Alloy. Journal of C.C.I.T., VOL.39, NO.1, May 2010

[10] Kamal Jangra, Sandeep Grover and Aman Aggarwal (2011) Simultaneous optimization of material removal rate and surface roughness for WEDM of WCCo composite using grey relational analysis along with Taguchi method, International Journal of Industrial Engineering Computations 2 (2011) 479–490

AUTHORS

First Author – P.JAGANATHAN M.E, Research scholar,

Department of Mechanical Engineering, Coimbatore institute of

technology, Coimbatore -641014,

jaganperiyasamy2009@gmail.com

Second Author – T.NAVEEN KUMAR M.E,

Asst. professor, Department of Mechanical Engineering, RVS

Faculty of Engineering, Coimbatore-641402,

naveethiru@gmail.com

Third Author – Dr.R.Sivasubramanian, Professor, Department

of Mechanical Engineering, Coimbatore Institute of Technology,

Coimbatore 641014,